Preparation of NIR‐II Polymer Nanoprobe Through Twisted Intramolecular Charge Transfer and Förster Resonance Energy Transfer of NIR‐I Dye

Abstract

AbstractNear‐infrared‐II (NIR‐II) fluorescence imaging is pivotal in biomedical research. Organic probes exhibit high potential in clinical translation, due to advantages such as precise structure design, low toxicity, and post‐modifications convenience. In related preparation, enhancement of NIR‐II tail emission from NIR‐I dyes is an efficient method. In particular, the promotion of twisted intramolecular charge transfer (TICT) of relevant NIR‐I dyes is a convenient protocol. However, present TICT‐type probes still show disadvantages in relatively low emission, large particle sizes, or limited choice of NIR‐I dyes, etc. Herein, the synthesis of stable small‐sized polymer NIR‐II fluoroprobes (e.g., 7.2 nm), integrating TICT and Förster resonance energy transfer process to synergistically enhance the NIR‐II emission is reported. Strong enhanced emissions can be obtained from various NIR‐I dyes and lanthanide elements (e.g., twelvefold at 1250 nm from Nd‐DTPA/IR‐808 sample). The fluorophore provides high‐resolution angiography, with high‐contrast imaging on middle cerebral artery occlusion model mice for distinguishing occlusion. The fluorophore can be rapidly excreted from the kidney (urine ≈65% within 4 h) in normal mice and exhibits long‐term renal retention on acute kidney injury mice, showing potential applications in the prognosis of kidney diseases. This development provides an effective strategy to design and synthesize effective NIR‐II fluoroprobes.